Hydrochloric Acid → 2-(4-Chlorobenzoylamino)-3-(oxindol-3-yl)propionic acid monohydrate

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Reaction Steps

6.8 Grams of 2-(4-chlorobenzoylamino)-3-(indol-3-yl)propionic acid prepared in Reference Example 6 was suspended in 8 g of dimethyl sulfoxide, then 17 g of concentrated hydrochloric acid was added to the suspension, and the resulting mixture was stirred at a room temperature for 2 hours. Further, 80 ml of water was added to the reaction mixture and stirred at a room temperature for 1 hour. The crystals formed were collected by filtration, washed with water, and dried. The crude crystals thus obtained were suspended in a mixture of chloroform:methanol=50:1 and stirred, the crystals were collected by filtration, and dissolved in a saturated sodium bicarbonate aqueous solution. The insoluble materials were removed by filtration, the filtrate obtained was neutralized with 10%-hydrochloric acid. The crystals formed were collected by filtration, washed with water, dried to obtain 3.2 g of 2-(4-chlorobenzoylamino)-3-(oxindol-3-yl)propionic acid monohydrate.

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